Commercial beverage cans are typically formed of two pieces: a drawn and wall-ironed (“DWI”) body and an end or lid seamed onto the open end of the can body. In the DWI process for forming a can body, a circular blank is first cut from a sheet of a 3000 series aluminum alloy, such as 3004 having the following properties according to (ASTM B209-14):
Aluminium: 95.6 to 98.2% (or remainder after the limits below)
Copper: 0.25% max
Iron: 0.7% max
Magnesium: 0.8 to 1.3%
Manganese: 1.0 to 1.5%
Silicon: 0.3% max
Zinc: 0.25% max
Residuals: 0.15% max
The blank is drawn into a cup in a machine referred to as a cupper. The drawing process typically does not change the thickness of the material, such that the sidewall and base of the cup have the same or nearly the same thickness as the blank.
The cup is then transferred into a machine referred to as a bodymaker, in which a cylindrical ram is inserted into the open end of the cup in a close fit. The ram them pushes the cup through a series of circular dies. Each die has an opening diameter that is slightly less than the outside diameter of the metal of the cup. Thus the metal is “ironed” in each die, which thins and elongates the sidewall. At or near the end of the ironing stages, the ram pushes the can body onto doming tooling, which deforms the flat can bottom into a dome and forms the foot. The most popular size of commercial beverage cans have a dome having a thickness of approximately 0.010 inches thick. In most circumstances, the bottom of the can is structurally complete at the end of the bodymaking operation.
After the bodymaker, the can body typically goes through operations that form a neck and a flange on the open end of the can. The can body before filling with the product is coated with a conventional lacquer to provide a barrier between the liquid product and the aluminum.
The end or lid is typically formed of a 5000 series aluminum alloy in a shell press that forms a circular blank into a shell and a conversion press that attaches the tab to the shell. After filling, an end is positioned on the can body such that the peripheral curl structure of the end is aligned with the can body flange. The both the end and the can body are mutually deformed to form the seam.
The internal pressure in a beverage can typically is from gas entrained in the liquid product, or generated from liquid nitrogen dosing prior to seaming the container.
It has been a longstanding focus of DWI beverage can manufacturers to make the can lightweight and structurally intact, even when the can is under pressure and is given rough handling.
Aerosol cans typically are made of three pieces: a domed end that is fitted with a dispensing valve, a cylindrical body that is open on each end, and a shallow bottom end. The can body is typically formed by rolling a flat sheet of tinplate steel and welding the ends together to form a longitudinal joint. The bottom end and domed ends are seamed onto the open ends of the welded cylinder.
Aerosol cans typically have a valve in the top component of the can, which is used for charging the can with propellant. Alternatively a grommet that is located in an aperture in the domed base, may be used for charging the can with a propellant, which typically is a volatile hydrocarbon. The grommet in the domed base is used when the product and the propellant must remain separate. For example, popular commercial systems, referred to bag-in-can or bag-on-valve, use a pouch or bag that holds the product while the propellant surrounds the bag. Some applications use a piston barrier to separate the product from the propellant, such as technology marketed under the tradename Earthsafe™ by a sister company of the present assignee.
Several conventional grommets are commercially available for charging aerosol cans with propellant, as will be understood by persons familiar with technology of charging aerosol cans. In a conventional aerosol can, an aperture is formed in the bottom end before the end is seamed onto the cylindrical can body. Because the aperture is formed in the unattached end, opposing tools have easy access to contact the upper and lower surfaces of the end. The grommet can then be installed into the aperture from either the topside or underside of the end before seaming onto the can body.